A pipeline inspection system includes a pipeline pig having a controller and a plurality of ultrasonic transducer elements situated in an array. Each of the plurality of ultrasonic transducer elements emits an ultrasonic signal into a wall of a pipeline and receives echoes of the ultrasonic signal from the pipeline wall. The controller selects a first subset of the plurality of ultrasonic transducer elements from which to emit the ultrasonic signals into the wall of the pipeline as the pipeline pig passes through the pipeline, analyzes the echoes of the ultrasonic signals received by the plurality of ultrasonic transducer elements to detect a feature in the pipeline wall, and selects a second subset of the plurality of ultrasonic transducer elements to emit the ultrasonic signals into the wall of the pipeline as the pipeline pig passes through the pipeline when the feature is detected in the pipeline wall.